KR830002563B1 - Process for preparing tetrahydrofuran - Google Patents

Abstract

THF production comprises reducing an aldehyde ether of formula (I) to form a hydroxyether of formula (II). (II) is then cleaved under dehydrating conditions to form THF, which is then recovered. R1 and R2 are 1-4C alkyl; R3 and R4 are H or 1-3C alky1. Alternatively R2 and R3 may form, together with their common C atoms, a 5- or 6-membered cycloaliphatic ring. Pref. (I) is obtained by reacting an ally1 t-alky1 ortycloalky1 ether of formula (III) under hydroformulation conditions, with CO and H2 in the presence of a hydroformulation catalyst. 2-hydroxytetrahydrofuran is not used as an intermediate.

Description

Method for producing tetrahydrofuran

The present invention relates to a method for producing tetrahydrofuran.

U. S. Patent No. 4,064, 145 discloses a method for producing tetrahydrofuran by hydroformylating allyl alcohol using a rhodium complex catalyst, followed by aqueous extraction to recover 4-hydroxy butanal, and hydrogenation under acidic conditions. Described.

However, the disadvantages of the process for producing tetrahydrofuran are the use of allyl alcohol under hydroformylation conditions, the formation of by-products of propanol as hydrogenated hydrogen, and the propion aldehyde isomerization. Moreover, hydroformylation of allyl alcohol is complicated by the very rapid inactivation of the rhodium complex catalyst which can be caused as a byproduct of the reaction. In addition, 4-hydroxy butyraldehyde, the desired intermediate product, is a 2-hydroxy tetrahydrofuran which is rather difficult to convert into butane-1 and 4-diol by opening and reducing before the formation of tetrahydrofuran occurs. It is formed naturally and tends to be internal aldolized. Despite these reasons, the preparation of tetrahydrofuran by a method including hydroformylation of allyl alcohol involves difficulties.

Accordingly, the present invention provides a method capable of converting to allyl alcohol tetrahydrofuran by a method comprising a hydroformylation step to essentially avoid the risk of catalyst inactivation due to the inert effect following the hydroformylation of allyl alcohol. do.

In addition to not using 2-hydroxytetra hydrofuran as an intermediate product according to the present invention there is provided a process for preparing tetrahydrofuran from allyl alcohol comprising a hydroformylation step.

According to the present invention, there is provided a process consisting of reducing aldehyde-ether of the following general formula (1) to produce hydroxy-ether of the following general formula (2) and decomposing it to produce tetrahydrofuran.

According to the invention, it is also possible to convert allyl alcohol to allyl t-alkyl or cycloalkyl ether of the following general formula (3), which is converted to the aldehyde-ether of the following general formula (1) with carbon monoxide and hydrogen in the presence of a hydroformylation catalyst. It was prepared, and the obtained aldehyde-ether was reduced to form the corresponding hydroxy-ether of the following general formula (2), and to decompose it under dehydration conditions to provide a method for producing tetrahydrofuran.

In General Formulas (1)-(3), R ₂ represents a methyl or ethyl group, respectively, R ₃ is preferably a hydrogen atom or a methyl group, and R ₄ is preferably a hydrogen atom. In a particularly preferred method, R ₁ and R ₂ each represent a methyl group and R ₃ and R ₄ each represent a hydrogen atom.

The preparation of the aldehyde ether of general formula (1) is described in more detail in patent application 1484/80 of the same applicant as the present application.

Decomposition of the hydroxy-ether of the general formula (2) yields the olefin of the following general formula (4).

Wherein R ₁ , R ₂ , R ₃ and R ₄ are as follows.

The etherification of allyl alcohol can be conveniently carried out by reacting with an olefin of the general formula (4) in the presence of an acid catalyst. Etherification is a reversible reaction and is facilitated by using a low temperature, such as a temperature in the range of about 0 ° C-80 ° C. Usually, etherification of allyl alcohol is preferably performed at about 60 ° C. or lower, preferably about 15 ° C.-60 ° C. such as about 35 ° C.-60 ° C. Since olefins are volatile, it is necessary to carry out the etherification reaction under elevated pressure. Typical acid catalysts are, for example, aqueous acids such as aqueous phosphoric acid or dilute solutions of sulfuric acid (e.g. containing 10% w / v or less sulfuric acid), acid zeolites, acid clays, and organic acids such as P-toluene sulfonic acid or formic acid. As well as ion exchange resins (preferably in the form of anhydrides) containing sulfonic acid and / or carboxylic acid groups such as Amberlyst 15 and Dowex 50 resins.

Formula (2) because of a preferred method for converting allyl alcohol to allyl t-alkyl or cycloalkyl ethers of formula (3), consisting of reacting allyl alcohol with olefins of formula (4) in the presence of an acid catalyst. The olefin of formula (4) due to the decomposition of hydroxy-ether of can be recycled to the allyl t-alkyl or -cycloalkyl ether formation step.

The tertiary alcohol of the following general formula (5) can be prepared as a byproduct upon decomposition of the hydroxy-ether of general formula (2).

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are as described above).

These alcohols of formula (5) are in the presence of an acid catalyst to produce the corresponding olefins of formula (4) which can be recycled for use in the preparation of allyl t-alkyl or cycloalkyl ethers of formula (3). Can be dehydrated.

The decomposition of the hydroxy-ether of formula (2) can be carried out in the presence of a suitable acid catalyst. Examples of acid catalysts for use in ether formation and decomposition include acidic ion exchange resins, acid clays, acid aluminas, acid aluminosilicates, and silicas, as well as aqueous acids such as aqueous phosphoric acid or sulfuric acid.

The decomposition of the hydroxy-ether of general formula (2) can be carried out under dehydration conditions. Such conditions consist, for example, of contacting the hydroxyether of formula (2) with an acid catalyst at a time and temperature sufficient to dehydrate and cyclize. Thus, the present invention allows the hydroxy ether of the general formula (2) to be contacted for a long time at an acid catalyst and / or at an elevated temperature, especially at a temperature of 100 ° C. or higher, such as 160 ° C. or higher, such as about 180 ° C. The decomposition of the hydroxy-ether of formula (2) can form butane-1,4-diol, especially under relatively mild conditions. Although butane-1,4-diol is a useful by-product of the decomposition step in many instances, it is desirable to select conductive conditions to drive dehydration-reaction as far as possible during the decomposition step. Butane-1, 4-diol prepared in the decomposition step can be recycled to the decomposition step for dehydration and cyclization for tetrahydrofuran if not required as a product. The catalysts and conditions necessary to obtain a tetrahydrofuran: butane-1,4-diol production ratio that can be tolerated during the decomposition step are described in "Self-directing optimization" (see Technometrics, November 1962). You can easily decide this way.

In the decomposition step, the diether of the following general formula (6) may be formed as a by-product.

It can be recycled advantageously in the decomposition step in which it decomposes itself to form other hydroxy-ethers of formula (2) and / or tetrahydrofuran and olefins of formula (4).

Recovery of the tetrahydrofuran product can be carried out by conventional methods of melanoma. For example, distillation or washing of the reaction product mixture may be used when the decomposition of the hydroxy ether of formula (2) is treated with an acidic ion exchange resin. On the other hand, when an aqueous acid is used for ether decomposition, the aqueous layer contains a large amount of tetrahydrofuran and can be recovered by neutralization and distillation.

The method of reducing the aldehyde ether of general formula (1) to the hydroxy-ether of general formula (2) may be carried out by contact hydrogenation, for example, under atmospheric pressure, sub-atomospheric pressure, or over atmospheric pressure. The reduction is preferably carried out under conditions in which no ether decomposition can occur. It is therefore desirable to avoid acidic conditions in the reduction step. Raney nickel is a suitable hydrogenation catalyst. The hydrogenation can be carried out at room temperature, near room temperature or at elevated temperatures, such as about 15 ° C.-120 ° C. or higher, such as up to about 180 ° C. Included are copper chromite and palladium hydrogenation catalysts as well as supported metal hydrogenation catalysts commercially useful in other hydrogenation catalysts. Reduction with sodium borohydride or lithium aluminum hydride is also possible.

When using solid catalysts such as nickel or other metals supported on granular carriers, the dropping phase system can be used to pass hydrogen and aldehyde-ethers of general formula (1) over the catalyst.

Examples of hydrogenated catalysts include commercial catalysts such as pto ₂ , pd / C, pt / Al ₂ O _3, and Girdler G 69 catalysts. Pressures up to 15 kg / cm ² absolute or higher may be used.

In the hydroformylation step, the hydroformylation catalyst may be a Group 8 metal-containing hydroformylation catalyst known to be effective for catalyzing the hydroformylation of terminal olefins. Preferred catalysts are preferably rhodium containing catalysts consisting of rhodium complexed with triorganic phosphine ligands such as carbon monoxide and triphenylphosphine. When using such a catalyst, the concentration of rhodium in the reaction medium may be in the range of about 5 ppm (weight) -1,000 ppm of rhodium or higher calculated as rhodium metal. Typical rhodium concentration ranges are about 20 ppm-400 ppm, such as about 40-300 ppm, calculated as rhodium metal. The reaction medium may comprise an excess of triorganophosphines, such as about 2 mol-100 moles or more of excess free triorganophosphines per gram atom of rhodium. Typically the hydrogen: carbon monoxide molar ratio is approximately 1: 1, such as about 1.05: 1. Typically, hydroformylation conditions include reaction temperatures of about 20 ° C.-160 ° C. such as about 70 ° C.-120 ° C. and about 0.1 kg / cm ² (absolute) to about 10 kg / cm ² (absolute) or higher hydrogen partial pressures and about Use of 0.1 kg / cm ² (absolute) —about 10 kg / cm ² (absolute) or higher carbon monoxide partial pressure is included. The total pressure may be about 20 kg / cm ² or less. The reaction can be carried out in the presence of a solvent, such as a mixture of aldehyde condensation products as described in British Patent No. 1,338,237, or without the addition of a solvent. The aldehyde-ether of formula (1) may be recovered from the hydroformylation reaction medium by conventional methods such as distillation.

The byproduct in the hydroformylation step is the corresponding iso-aldehyde ether of the following general formula (7).

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are as described above).

Iso-hydroxy- of the following general formula (8) without separation from the aldehyde-ether of general formula (1), or from the corresponding reduction product before the reduction step, ie from the hydroxy-ether of general formula (2) before the decomposition stage Ether can be separated.

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are as described above).

In this case, the by-product of the decomposition step is 2-methylpropane-1, 3-diol. Another by-product of the decomposition step may be the corresponding diether of the following general formula (9).

Therefore, when the intermediate purification is not carried out, in the decomposition step, the olefin of the general formula (4), the tertiary alcohol tetrahydrofuran of the general formula (5), the unreacted hydroxy ether of the general formula (2), and the general formula ( Iso-hydroxy-ether of 8), diethepes of formulas (7) and (9), butane-1, 4-diol, 2-methylpropane-1, 3-diol, and British Patent Specification No. 2,338,237 Complex reaction mixtures containing small amounts of small byproducts, such as complex aldehyde condensation products of the solvents described (derived from compounds of formulas (1) and (7)), can be obtained.

The hydroxy-ethers of formulas (2) and (8) and the diol-ethers of formulas (6) and (9) in this mixture are subjected to acid catalyzed decomposition to liberate the olefins of formula (4). Can be recycled advantageously to the decomposition step. The complex reaction mixture from the decomposition step can be separated by distillation of the various types of fractions in as many stages as possible (at least one stage can be kept under reduced pressure). Thus, when R ₁ and R ₂ are each methyl and R ₃ and R ₄ are each hydrogen, it can be distilled in a series of five steps, for example to separate the components of the crude reaction mixture from the decomposition step. In the first series of steps iso-butylene is recovered and the mixture of low boiling products containing t-butanol and tetrahydrofuran is recovered from the second series of steps. Tetrahydrofuran can be recovered from this mixture by redistillation. The mixture of the hydroxy-ethers of formulas (2) and (8) and the diol ethers of formulas (7) and (9) forms a government product from the third stage maintained under vacuum.

Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1

A. Preparation of Allyl t-Butyl Ether

50 ml of allyl alcohol and 5 g of anhydrous Ambelist 15 resin were placed in a 300 ml autoclave which was stirred by a Ma-gnedrive device operating an induction stirrer (“Ambelist” is a registered trademark). The autoclave was cleaned with iso-butylene and then warmed up to 30 ° C. in an oil bath and pressurized to 1.75 kg / cm ² (absolute) with iso-butylene. The pressure dropped as the reaction occurred and the pressure was further increased by 1.75 kg / cm ² by introducing more iso-butylene. This process was repeated as necessary until the reaction was complete after about 90 minutes as indicated by the stop of absorption of iso-butylene. After releasing the pressure the product was decanted from the resin and washed several times with deionized water. The crude product was partially vacuumed to remove iso-butylene (until iso-butylene became 0.1% or less in the product by gas chromatography) and then dried over anhydrous sodium carbonate. Gas chromatography using gas chromatography with flame ionization detector and temperature programming resulted in allyl t-butyl ether as an efficiency of 98% phase. The chromatography tower was made of 1.83 m × 3.2 mm OD stainless steel, filled with 10 wt% diethylene glycol succinate in chromosorb W.

B. Hydroformylation of Allyl t-Butyl Ether

The amount of calculations in the same autoclave, _{HRh (CO) (pph 3)} 3, and filled into pph ₃ and then sufficient pilmeo (Filmer) was added to 351 were the amount of the liquid up to 90ml (pilmeo 351 is described in British patent specification No. 1,388,237 No. Complex of the condensation product of n- and iso-butyraldehyde in a modified form, and then the autoclave was sealed The body of the autoclave was immersed in a heated oil bath and then heated by a heater / stirrer 40 The temperature in the reactor could be monitored by a pressure transducer connected to a single pen recorder.The stirrer was started and the speed was adjusted to 500r.pm. The reactor was cleaned with a hydrogen / carbon monoxide gas mixture, the composition was according to the planned H ₂ : CO ratio, and the reactor was then pressurized to level that 0.35 kg below the desired operating pressure. / cm ² and then separated The stirrer was adjusted to 2,000 rpm and the temperature increased to a predetermined value The pressure was increased to the required level using the same H ₂ / CO mixture and the reactor was then separated once again. Allyl t-butyl ether was added to the reactor and the reaction was initiated.The reaction rate was monitored by adjusting the pressure drop between two defined levels, ± 0.07 kg / cm ² , near the desired pressure. Upon reaching the reactor, the reactor is repressurized to a level of 0.14 kg / cm ² , the operating pressure planned to be about 1: 1 H ₂ : CO mixture, as required by the stoichiometric requirements of the reaction, and the process is continued until the reaction is complete. The pressure drop rate was negligible: the oil heater / stirrer was turned off, the hot oil was removed from the bath and replaced with cooling oil. Then the reactor was cooled again to engage the half-year of 40 ℃. Reactor agitator to turn off the power, in which the reactor pressure drop across the reaction solution was removed for analysis and then to open and / or storage.

Analysis of the reaction solution was carried out using the gas chromatography method summarized in A. Peak bands were calculated using integrators and mole selectivity was calculated from these results. The calculations used response factors measured from pure compounds separated from the reaction solution by preparative chromatography. The results are as described in the following table.

[table]

Note: TPP = triphenylphosphine

PTBE = propyl t-butyl ether

Trans-P (-) TBE) = trans-propen-1-yl t-butylether

ATBE = allyl t-butyl ether

Cis-P (=) TBE = cis-propen-1-yl t-butylether

TBMPA = 3-t-butoxy-2-methylpropionaldehyde

TBBA = 4-t-butoxy butyraldehyde

Reaction residues from these and other experiments were collected and distilled. 4-t-butoxybutyraldehyde was obtained as a colorless liquid.

C. Reduction of 4-t-butoxy Butyraldehyde

25 ml of 4-t-butoxy butyraldehyde and 2 g of raninickel were injected into a 300 ml stainless steel bump equipped with a stirrer, sealed, purged with nitrogen, purged with hydrogen, and 17.86 kg / cm with hydrogen. ² (absolute) compressions. The balm was heated to 75 ° C. and held at this temperature. The reactant aldehyde is smoothly hydrolyzed to 4-T-butoxy butanol in virtually quantitative manner. Upon completion of the reaction, the reaction solution was filtered by cooling the bomb and depressurizing and analyzed using the gas chromatographic technique described in section A above. The peak by the starting aldehyde virtually disappeared and a new peak appeared. The identity of this compound, such as 4-t-butoxy-butan-1-ol, was confirmed by ether decomposition to form tetrahydrofuran under dehydration conditions, as described below in part D.

D. Preparation of Tetrahydrofuran

10 ml of 4-t-butoxy butanol and 1 g of an anhydrous Amberlyst 15 acidic ion exchange resin prepared in Part C were charged to a 100 ml round bottom flask equipped with a magnetic stirrer, a sorting column and a distillation cooler. It was. The flask was heated to 120 ° C. for 4 hours using an oil bath. The gas is released to collect the light distillate which is initially inert at 64 ° C. The boiling point gradually rises to 98 ° C. as the reaction ends. The offgas was analyzed by gas chromatography using a column containing 20% by weight of diethyl succinate on Celite and was identical to iso-butylene. 5.4 g of distillate were collected where most of the organic components were identical to t-butanol and tetrahydrofuran by the gas chromatography method discussed in Section A. The residue in the flask was 0.5 g. The distillate was re-bulked into residue and reanalyzed and the results are described below.

Example 2

A. Hydroformylation of Allyl t-Butyl Ether

0.10 g of rhodium hydridocarbonyl tris- (triphenylphosphine), i.e., a stirrer with magnetic coupling of RhH (CO) (pph ₃ ) ₃ , 90 allyl t-butylether and 10.0 g of triphenylphosphine, It was loaded into a 300 ml autoclave equipped with a gas inlet tip tube and outlet valve. The autoclave was sealed and the contents were purged with nitrogen with stirring and then separated. Stirring was continued while raising the temperature of the autoclave by 73 ° C by immersing in an oil bath equipped with a thermostatically controlled heater-thermostat. The autoclave was purged with a 1: 1 mol H ₂ : CO mixture and then pressurized to 2.1 kg / cm ² (absolute) by closing the outlet valve. The reaction was initiated and proceeded slowly with exotherm at the beginning of the reaction. The pressure was strong as the reaction proceeded, and when the total pressure reached 1.9 kg / cm ² (absolute), the 1: 1 H ₂ : CO mixture was added to the autoclave to restore the pressure to 2.1 kg / cm ² (absolute). This repressurization technique was repeated as needed until no more gas was absorbed (indicating that the reaction was complete). This process takes 3-4 hours. The autoclave was cooled, the pressure dropped and then opened, the contents removed and stored under nitrogen.

The obtained solution was analyzed by gas chromatography using a tower filled with 10% W / W diethylene glycol succinate on helium and chromosob PAW and a flame deionization detector as a carrier gas. Selectivity was observed as follows.

5.6% for isomerized / hydrogenated allyl feedstock

18.9% relative to 3-t-butoxy-2-methylpropionaldehyde (TBMPA)

75.5% relative to 4-t-butoxy butyraldehyde (TBBA)

These selectivity is expressed in mol%.

Two aldehyde-ethers (TBMPA and TBBA) were separated by distillation from the other components of the reaction solution and then purified by distillation and characterized by the formation of dimedone derivatives and measurement of physical data. The following results were obtained.

Boiling point: 151.6 ℃ 169.5 ℃ at 743mmHg

152.3 ℃ 170.5 ℃ at 760mmHg

103.2 ℃ 115.6 ℃ at 100mmHg

Nuclear magnetic resonance spectra were obtained using tetramethylsilane as an internal standard and carbon tetrachloride as a solvent for the following compounds.

In each case the ratio of peak bands corresponded to the predetermined ratio as predicted from the respective structural formulas. For doublets, triplets, and multiplets, the chemical shifts quoted are median.

B. Hydrogenation of t-butoxy Butyr Aldehyde

25 ml of the reaction solution and 1.5 g of Ranickel from Section A of this Example were charged to a 300 ml capacity stainless steel baffle equipped with a magnetically coupled stirrer and inlet and outlet gas tubes and valves. The contents were stirred and pressurized with hydrogen to 14.1 kg / cm ² (absolute). After heating the bamboo to 70 ° C. in the jade, this temperature can be changed to a thermo-stirrer controlled by a thermostat. The pressure was maintained at 14.1 kg / cm ² (absolute) by adding hydrogen as needed. The reactor pressure is controlled using a downstream pressure regulator and a pressure transducer connected to the recorder. When the gas was no longer taken, the balm was cooled and its contents released and filtered. Gas chromatographic analysis using the technique described in Section A for this example indicated that quantitative hydrogenation actually occurred and the results are shown in the following table.

Note: 3-OH MPTBE = 3 = hydroxy-2-methylpropyl t-butylether

4-OH BTBE = 4-hydroxy butyl t-butyl ether

The structure of 3-OH MPTBE and 4-OH BTBE can be determined for the hydrogenated product by analysis of the degradation products prepared in the following C.

C. Preparation of Tetrahydrofuran

Another sample of allyl t-butyl ether was hydroformylated in a similar manner as described in part A of this example and separated by distilling the mixture of TBMTA and TBBA from the reaction mixture.

The hydrogenated mixture obtained has the following analysis as measured by gas chromatography.

31.05% by weight 3-OH MPTBE

65.58 wt% 4-OH BTBE

8.73 g of the present compound and 0.4 g of Abelist 15 resin were loaded into a 50 ml bottomed round flask equipped with a septum mounted side arm and also a vertical air cooler to facilitate testing. The top of the air cooler was equipped with a side arm connected to a thermometer and a cooler supplied with a coolant at -5 ° C, which was connected to a collection plaque with side arms leading to a Drechsel bottle containing water. The contents of the flask were magnetically stirred and heated to 120 ° C. on an oil bath. Reflux is initiated in the collection flask and the distillate is formally collected. The gas was released and found to be the same as iso-butylene by gas chromatography. After 16 hours the flask was cooled and the distillate was weighed and analyzed by gas chromatography. The distillate was 2.89 g in total and showed 83.6% water-equivalent correspondence of 4-OH BTBE in the starting material containing tetrahydrofuran (81.8% w / w) and t-butanol.

Example 3

A. Preparation of Allyl 2-methylbut-2-yl Ether

A 1 l volume bottom with 100 g 2-methylbut-2-ene, 300 g allyl alcohol and 10 g Amblylist 15 resin containing a magnetic follower and a gas inlet tube immersed below the surface of the liquid in the flask Equipped with a flat flask. The flask was purged with nitrogen and placed in a 30 ° C. water bath on a magnetic stirrer. The flask was kept at this temperature for 16 hours and then filtered. After washing 5 times with deionized water (every 1: 1 volume ratio), the organic layer obtained was dried over anhydrous sodium carbonate and then ether was purified by distillation in order to remove unreacted allyl alcohol.

Yield: 137g (74.9% based on olefin) Boiling Point: 125-127 ℃ at 770mmHg

B. Hydroport Millation of Aryl-2-methylbut-2-yl Ether

According to the hydroformylation process of Example 2, using 90 ml of allyl 2-methylbut-2-yl ether as feedstock instead of allyl t-butyl ether yielded the following selectivity (mol%).

7.4% for isomerization / hydrogenation feedstock

19.4% (MBMPA) relative to 3- (2'-methylbutane-2'-oxy) -2-methylpropionaldehyde

] 73.2% (MBBA) relative to 4- (2'-methylbutane-2'-oxy) -butyraldehyde

C. Hydrolysis of 4- (2'-Methylbutane-2'-oxy) -butyraldehyde

The following selectivity was obtained by the process of part B of Example 2 using 25 ml of the reaction shaft obtained in part B of this example as a starting material.

D. Preparation of Tetrahydrofuran

The crude hydrogenated mixture from part C was analyzed by gas chromatography and showed the following composition.

16.25% by weight of 3- (2'-methylbutane-2'-oxy) -2-methylpropane

67.6% by weight of 4- (2'-methylbutane-2'-oxy) -butanol (4-MBOB)

Except for using 8.29 g of the crude hydrogenated mixture as a starting material, the concentration of tetrahydrofuran in the distillate of 5.27 g was 39.2% w / w, except that 8.29 g was used. Corresponding to 81.8% sool based on 4-MBOB in starting material. In addition to tetrahydrofuran, the main product of distillate was 2-methylbut-2-ene.

Example 4

A. Preparation of Allyl 2, 3-dimethylbut-2-yl Ether

The process of Example A was repeated using 100 g of 2,3-dimethylbut-2-ene instead of 100 g of 2-methylbut-2-ene. As a result, 88 g of allyl 2,3-dimethylbut-2-yl ether (52.1% based on olefin) were obtained.

Boiling point: 144-147 ° C. at 765 mm Hg.

B. Hydroformylation of Allyl 2, 3-Dimethylbut-2-yl Ether

The hydroformylation process of Example 2 was repeated using 90 ml of allyl 2, 3-dimethylbut-2-yl ether instead of allyl-t-butylether. The obtained selectivity (mol%) was as follows.

6.0% against isomerized / hydrogenated allyl feedstock

19.3% relative to 3- (2 ', 3'-dimethylbutane-2'-oxy) -2-methylpropionaldehyde

74.7% relative to 4- (2 ', 3'-dimethylbutane-2'-oxy) -butyraldehyde.

C. Hydrolysis of 4- (2 ', 3'-dimethylbutane-2'-oxy) -butyraldehyde

The following selectivity was obtained in the process of part B of Example 2 using 25 ml of the reaction solution obtained in part B of this example as starting material.

D. Preparation of Tetrahydrofuran

The crude hydrogenated mixture from part C was analyzed by gas chromatography and showed the following composition.

15.5% by weight of 3- (2 ', 3'-dimethylbutane-2'-oxy) -2-methylpropanol

65.1% by weight of 4- (2 ', 3'-dimethylbutan-2'-oxy) -butanol (4DiMBOB)

The concentration of tetrahydrofuran in the distillate, which was 6.22 g, was 35.5% w / w, except that 8.86 g of the hydrogenated mixture was used as starting material, according to the method described in part C of Example 2. Corresponding to 87.2% yield based on 4DiMBOB in starting material. In addition to tetrahydrofuran, the main product in the distillate was 2, 3-dimethylbut-2-ene.

Example 5

A. Preparation of Allyl 1-methylcyclohexyl Ether

The process of Example A was repeated using 100 g of 1-methylcyclohexene as the olefin instead of isobutylene. The yield of allyl 1-methylcyclohexyl ether was 93.5 g (58.3% based on olefin).

Boiling point: 138-140 ° C. at 240 mmHg.

B. Hydroformylation of Allyl 1-Methylcyclohexyl Ether

As a feedstock in the hydroformylation process of Example 2, 90 ml of allyl 1-methylcyclohexyl ether was used. The selectivity (mol%) was as follows.

8.0% for isomerized / hydrogenated allyl feedstock

19.0% relative to 3- (1'-methylcyclohexaneoxy) -2-methylpropionaldehyde

73.0% relative to 4- (1′-Methylcyclohexaneoxy) -butyraldehyde.

C. Hydrocracking of 4- (1-methylcyclohexaneoxy) -butyraldehyde

Using 25 ml of the reaction solution obtained in Part B of this example as a starting material, the following results were obtained in the process of Part B of Example 2.

D. Preparation of Tetrahydrofuran

The crude hydrogenated mixture from part C was analyzed by gas chromatography and showed the following composition.

17.7% by weight of 3- (1'-methylcyclohexaneoxy) -2-methyl propanol

65.7 wt% of 4- (1'-methylcyclohexaneoxy) -butanol (4-MCHB)

Aside from using 3.16 g of the above hydrogenated mixture as a starting material, the procedure described in section C of Example 2 was followed to find that the concentration of tetrahydrofuran in 2.335 g of distillate was 78.8% w / w. Corresponding to 88.7% yield based on 4-MCHB in starting material. In addition to tetrahydrofuran, the main product in the distillate was 1-methylcyclohexane.

Example 6

Aside from cooling the collection flask with a "dry ice" / iso-propanol trap, a mixture of 100 g of 3-OH MPTBE and 4-OH BTBE was treated by the method described in part C of Example 2. The collected iso-butylene is used to make further allyl t-butyl ether, and then purified and subsequently hydroformylated according to the process described in part A of Example 2, whereby It has been demonstrated that olefins of formula (4) formed by decomposing hydroxyether can be recycled to the step of forming allyl ethers of formula (3).

Example 7

The following components were loaded in the same autoclave used in Example 2.

Using the process described in A of Example 2, the reaction process was detected at 73 ° C. using a 1: 1 H ₂ : CO mixture at a total pressure of 4.22 kg / cm ² (absolute). Analysis of the reaction solution when gas inhalation was stopped showed that almost allyl t-butylether reacted.

In contrast, substitution of 90 ml of allyl t-butylether with 90 ml of allyl alcohol showed that the reaction proceeded up to 36% conversion before gas intake was effectively stopped, indicating that in fact the entire deactivation of the catalyst occurred.

Claims (1)

As described above in the text, a method for preparing tetrahydrofuran consisting of reducing the aldehyde-ether of the following general formula (1) to produce a hydroxy ether of the following general formula (2) and decomposing it under dehydration conditions.